The present invention is directed to active structural vibration control. More particularly, this invention is a flexibly-mounted Active Vibration Absorber (AVA).
In the realm of active noise and vibration control, there are three implementation approaches: active noise control, which uses an inverse-phase sound wave to cancel the disturbance signal; active structural control, which vibrates a structural component at a frequency to cancel the input disturbance (noise and/or vibration); and active isolation control, where an actuator in a mount is reciprocated at the proper frequency, phase and amplitude to cancel the input disturbance (which, again, may be a structural vibration or in the audible range, in which case it is experienced as noise). The active tuned AVA falls in the category of active structural control.
Tuned vibration absorbers are known. These are generally passive systems in which the mass M.sub.2 is chosen to resonate at or near the primary frequency of interest, e.g., the blade pass frequency of a helicopter rotor. The problem with such passive absorber systems has been that the weight penalty paid for their usage was not justified by the level of improvement in performance. Further, the performance was limited by the fact that once the mass was chosen, its effectiveness was restricted to optimization at a single frequency. The system was unable to adapt to changing conditions in order to cancel other frequencies.
The present invention enhances the performance of an active tuned absorber by flexibly-mounting the AVA. Multiple embodiments are shown for shaping the output spectrum of the AVA by various embodiments of flexible-mountings. Further, in another aspect, means for counterbalancing the flexibly-mounted AVA are described.
Various other features, advantages and characteristics will become apparent after a reading of the following specification.